The present invention generally relates to water heaters and, in illustrated embodiments thereof, more particularly relates to a specially designed foam dam structure used to shield electrical or other types of components or structures projecting outwardly from the storage tank portion of the water heater from insulating foam injected into an insulation space surrounding the tank and disposed between the tank and an outer metal jacket portion of the water heater.
Modern water heaters of both the electric and fuel-fired type typically include a storage tank portion adapted to hold a quantity of water, previously heated by a heating system portion of the water heater, for on-demand supply to various plumbing fixtures such as sinks, tubs, showers and the like. To improve the thermal efficiency of the water heater, and lower its energy usage cost, the tank is typically insulated by injecting a hardenable, initially liquid foam insulation material into an insulation space that outwardly surrounds the tank and is disposed between the outer tank surface and a metal jacket structure spaced outwardly apart from the tank.
Various electrical components, such as thermostats and electric heating elements, or other types of structures such as pipe coupling fittings, typically project outwardly from the exterior side surface of the tank and underlie one or more jacket openings that provide access to such electrical components or other structures. Because the electrical components or other outwardly projecting structures are disposed within the insulation space surrounding the tank, they must be appropriately protected from exposure to liquid foam insulation being injected into the insulation space. Additionally, each jacket opening must be appropriately sealed at its periphery to prevent injected liquid insulation foam material from being forced outwardly through the jacket openings.
A commonly utilized approach to shielding an electrical component, or other structure projecting outwardly from the tank, from liquid insulation being forced into the jacket/tank insulation space, and to prevent injected foam from being forced outwardly through the associated jacket opening overlying the electrical component or other structure, is to install a shielding/sealing structure commonly referred to as a foam dam. The typical foam dam is basically a hollow structure having opposite open inner and outer sides and which is installed within the jacket/tank insulation space, around the electrical component or other structure which underlies the jacket opening, in a manner causing the dam to circumscribe the electrical component or other structure, the open inner side of the dam to form a seal against the tank, and the open outer side of the dam to seal around the periphery of the associated tank opening. During the subsequent injection of the liquid foam insulation into the jacket/tank insulation space the installed dam structure sealingly shields the electrical component or other structure from contact with the incoming foam and also prevents the pressurized foam from being forced outwardly through the jacket opening.
Conventional foam dams of this general type have associated therewith a variety of problems, limitations and disadvantages. One previously proposed technique for shielding structures projecting outwardly from a water heater tank into the jacket/tank insulation area, and for preventing injected insulation leakage outwardly through the associated jacket opening, is to carefully fit a fiberglass block structure against the tank exterior around the structure to be shielded from injected insulation, and then install the jacket structure over the outer side of the block. During subsequent injection of the insulating foam the fiberglass block serves as a barrier within the enclosed insulating space to prevent the foam from being forced out through the jacket structure opening or into contact with the outwardly projecting structure being shielded by the block.
While this is a relatively simple and straightforward approach to forming foam stop barriers, it has two primary disadvantages. First, the fiberglass block must be very carefully sized to sealingly extend between the outer surface of the water heater storage tank and the inner surface of the jacket structure. If even a slight gap exists around the installed block it can easily permit the injected foam to escape from the jacket structure and/or come into contact with the outwardly projecting structure shielded by the block. Second, the fiberglass block, which tends to be relatively large, typically has a thermal insulation value substantially less than that of the insulating foam. Accordingly, relative to the foam insulation, the fiberglass block forms a relatively low resistance heat outflow path in the assembled water heater. As energy conservation goals and standards continue to increase, this situation becomes less and less acceptable.
Another method conventionally used to form a foam stop barrier around an electrical component or other structure projecting outwardly from a water heater storage tank is to construct a relatively flat, foam-filled bag having one or more openings therein through which the outwardly projecting structure to be shielded may be extended, taping the bag blanket-like to the tank exterior, and then installing the outer jacket structure over the bag. Since the bags are filled with foam insulation, they do not present the heat leak problem that the fiberglass blocks do. However, like the fiberglass blocks, the foam filled bags present the potential problem of injected foam leakage past the bags if they are not carefully sized and properly fitted into place within the enclosed insulation space before the foam injection process is initiated. Additionally, the bags are rather tedious and time consuming to fabricate and install, thus undesirably increasing the overall construction cost of the water heater.
In the water heater foam dam illustrated and described in U.S. Pat. No. 5,163,119 to Windon a hollow foam dam structure is provided which is insertable through a jacket opening to circumscribe electrical components which are to be shielded from subsequently injected insulating foam material. A separate component, namely an outer metal door secured to the jacket over the installed dam, compresses an outer side lip portion of the dam inwardly against the jacket to create the necessary seal between the dam and the jacket opening periphery. This outer door is installed over the dam, prior to initiating the insulation foaming process, to effect a tight seal between the lip of the dam and the jacket.
Additionally, in the foam dam illustrated and described in this patent it is necessary to use yet a second separate component, namely a cap which is wedged in and covers the open outer side of the installed dam, to provide the installed dam with sufficient rigidity around the entire circumference of the dam walls to adequately resist undesirable leak-creating deformation thereof caused by insulation injection pressure forces.
In view of the foregoing it can be readily seen that it would be desirable to provide a foam dam structure and associated installation methods which eliminate or at least substantially reduce at least some of the above-mentioned problems, limitations and disadvantages associated with conventional foam dam structures and installation methods of the types generally described above.